DESCRIPTION: (Applicant's Description) The need for repeated administration of anti-factors for long-term therapy of cancer makes gene therapy approaches particularly attractive because sustained expression of anti-angiogenic factors at the tumor site could be achieved. The ability to deliver the anti-angiogenic genes specifically and efficiently to the tumor site will be a key issue for future in vivo anti-angiogenic gene therapy. This exploratory project (R21) aims to design and produce, by using chemical modifications as primary means, retroviral gene transfer vectors that have specific infectivity for target tumor cells for in vivo anti-angiogenic gene therapy of cancer. We will use the retroviral gene transfer vectors, consisting of the viral core of spleen necrosis virus (SNV) and the SNV envelope glycoprotein, which have no infectivity for human cells. However, once these retroviral vectors are made capable of binding specifically to the surface of the target human cell, they can mediate efficient infection by using their natural infection capability. We will use a chemical approach, taking advantage of the extremely tight affinity between streptavidin and biotin, to attach a tumor-specific binding reagent to the surface of retroviral gene transfer vectors such that a tumor-specific infectivity can be generated. Glioma cells that over-express the human epidermal growth factor receptor (hEGFR) and monoclonal antibodies against the extracellular domain of hEGFR will be used as targets and binding mediators, respectively, to see if such modified retroviral gene transfer vectors can infect hEGFR-expressing cells specifically and efficiently. In particular, we will characterize, quantitatively, the degree of modification of the retroviral surface and how each of these modifications affects the binding specificity and infectivity of the modified retroviral gene transfer vectors for the glioma cells over- expressing hEGFR. We will then apply this strategy to SNV-based retroviral gene transfer vectors carrying the angiostatin and endostatin cDNA's to see if these genes can be delivered specifically to the target tumor cells over- expressing hEGFR and if they can be expressed efficiently in the tumor cells.